Following certain injuries, surgery or other medical treatments that affect the mobility of the knee, it is customary for the patient to be prescribed physical therapy. For example after knee operation, scar tissue may form in knee tissue (i.e. arthrofibrosis) and as such, mobility of the knee may suffer. For example, without rehabilitative therapy, a patient who has undergone knee surgery may not be able to walk properly or return to independent daily activities and could potentially suffer from back pain, hip pain, and knee pain.
Normal range of motion of the knee is considered to be 0° of extension and 135° degrees of flexion. For example, 0° of extension may be achieved by a person extending their knee such that their lower leg is parallel with their upper leg. An upper leg of a patient is also known as a thigh, and is defined as the area between a patient's pelvis and knee. For example, the upper leg usually includes the femur. On the other hand, a lower leg of a patient is defined as the part of the leg that lies between the knee and the ankle. The lower leg usually includes the fibula and the tibia. As another example, 135° of flexion can be achieved when a person flexes their lower leg such that an angle subtending their lower leg and their upper leg is 45°. Knee extension describes straightening of the lower leg relative to the upper leg, and knee flexion describes bending the knee such that an angle between the lower leg and the upper leg decreases. Hip extension described straightening the upper leg relative to the spine, and flexion is described as bending the hip joint such that the upper leg to spine angle decreases.